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Networking without an OS Josh Triplett josh@joshtriplett.org PyCon 2016

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Porting Python to run without an OS

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PyCon 2015 BIOS Implementation Test Suite (BITS) Python in GRUB and EFI, without an OS Explore and test hardware and firmware

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BITS Capabilities Interactive Python interpreter (with line editing and tab completion)

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BITS Capabilities Interactive Python interpreter (with line editing and tab completion) Direct access to hardware and physical memory

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BITS Capabilities Interactive Python interpreter (with line editing and tab completion) Direct access to hardware and physical memory Python can call EFI firmware protocols via ctypes

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BITS Capabilities Interactive Python interpreter (with line editing and tab completion) Direct access to hardware and physical memory Python can call EFI firmware protocols via ctypes Most of the Python standard library

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Most of the Python standard library

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Most of the Python standard library Some modules don’t make sense without an OS

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os.execve os.fork

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os.execve os.fork multiprocessing popen2 subprocess

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os.execve os.fork multiprocessing popen2 subprocess webbrowser

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import antigravity

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socket select

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socket select urllib2 httplib SocketServer BaseHTTPServer

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EFI networking protocols EFI_IP4_CONFIG2_PROTOCOL EFI_TCP4_PROTOCOL

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Why networking in firmware? Send scripts or test data into the machine

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Why networking in firmware? Send scripts or test data into the machine Read test data or logs from the machine

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Why networking in firmware? Send scripts or test data into the machine Read test data or logs from the machine Avoid relying on a writable filesystem

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Why networking in firmware? Send scripts or test data into the machine Read test data or logs from the machine Avoid relying on a writable filesystem Speed up edit/compile/boot/run cycle

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Demo

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Bridging EFI networking and Python sockets Could call EFI network protocols directly Want compatibility with existing Python networking code Python modules import socket and select socket (Python) imports _socket (C)

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Sockets overview “Berkeley” sockets

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Sockets overview “Berkeley” sockets Standard on UNIX/POSIX systems, and on Windows via WinSock

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Sockets overview “Berkeley” sockets Standard on UNIX/POSIX systems, and on Windows via WinSock Focusing exclusively on TCP/IP connections

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Creating a socket int s = socket(AF_INET, SOCK_STREAM, 0);

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Creating a socket int s = socket(AF_INET, SOCK_STREAM, 0); AF_INET - IP

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Creating a socket int s = socket(AF_INET, SOCK_STREAM, 0); AF_INET - IP SOCK_STREAM - TCP

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Creating a socket int s = socket(AF_INET, SOCK_STREAM, 0); AF_INET - IP SOCK_STREAM - TCP Can use s as either client or server socket

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Client socket socket

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Client socket socket connect

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Client socket socket connect struct sockaddr

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Client socket socket connect struct sockaddr send/recv

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Client socket socket connect struct sockaddr send/recv close

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Server socket socket

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Server socket socket bind

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Server socket socket bind struct sockaddr

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Server socket socket bind struct sockaddr listen

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Server socket socket bind struct sockaddr listen accept - returns a new connected socket

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Server socket socket bind struct sockaddr listen accept - returns a new connected socket send/recv

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Server socket socket bind struct sockaddr listen accept - returns a new connected socket send/recv close

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select - waiting for activity Pass sets of file descriptors to monitor for reading and for writing

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select - waiting for activity Pass sets of file descriptors to monitor for reading and for writing And for exceptions, but ignoring that here

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select - waiting for activity Pass sets of file descriptors to monitor for reading and for writing And for exceptions, but ignoring that here Pass a timeout

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select - waiting for activity Pass sets of file descriptors to monitor for reading and for writing And for exceptions, but ignoring that here Pass a timeout Waits for a connected socket to have data to recv or send

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select - waiting for activity Pass sets of file descriptors to monitor for reading and for writing And for exceptions, but ignoring that here Pass a timeout Waits for a connected socket to have data to recv or send Waits for a listening socket to have a connection

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select - waiting for activity Pass sets of file descriptors to monitor for reading and for writing And for exceptions, but ignoring that here Pass a timeout Waits for a connected socket to have data to recv or send Waits for a listening socket to have a connection Core of the main loop in most network servers

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select - waiting for activity Pass sets of file descriptors to monitor for reading and for writing And for exceptions, but ignoring that here Pass a timeout Waits for a connected socket to have data to recv or send Waits for a listening socket to have a connection Core of the main loop in most network servers Many OS-specific replacements for scalability and performance

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Python bindings import socket, select

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Python bindings import socket, select s = socket.socket() - defaults to TCP/IP

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Python bindings import socket, select s = socket.socket() - defaults to TCP/IP s.connect

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Python bindings import socket, select s = socket.socket() - defaults to TCP/IP s.connect s.bind, s.listen, s.accept

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Python bindings import socket, select s = socket.socket() - defaults to TCP/IP s.connect s.bind, s.listen, s.accept s.sendall, s.recv

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Python bindings import socket, select s = socket.socket() - defaults to TCP/IP s.connect s.bind, s.listen, s.accept s.sendall, s.recv rl,wl,xl = select.select([s],[],[]) if s in rl:

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CPython implementation socketmodule.c and selectmodule.c

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CPython implementation socketmodule.c and selectmodule.c Extensive dependencies on POSIX and on C sockets API

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CPython implementation socketmodule.c and selectmodule.c Extensive dependencies on POSIX and on C sockets API Would have to implement those APIs in C

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CPython implementation socketmodule.c and selectmodule.c Extensive dependencies on POSIX and on C sockets API Would have to implement those APIs in C Handle C arguments, addresses, buffer management

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CPython implementation socketmodule.c and selectmodule.c Extensive dependencies on POSIX and on C sockets API Would have to implement those APIs in C Handle C arguments, addresses, buffer management Would have to call EFI protocols from C

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CPython implementation socketmodule.c and selectmodule.c Extensive dependencies on POSIX and on C sockets API Would have to implement those APIs in C Handle C arguments, addresses, buffer management Would have to call EFI protocols from C Or, have many callbacks from C to Python

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BITS implementation C helper for safe asynchronous event handling Otherwise entirely Python Python makes all EFI protocol calls

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Calling EFI from Python via ctypes

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Behind the scenes efi.system_table is a data structure

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Behind the scenes efi.system_table is a data structure efi.system_table.ConOut is a pointer to a protocol

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Behind the scenes efi.system_table is a data structure efi.system_table.ConOut is a pointer to a protocol .contents dereferences a ctypes pointer

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Behind the scenes efi.system_table is a data structure efi.system_table.ConOut is a pointer to a protocol .contents dereferences a ctypes pointer Most EFI calls expect a “this” pointer

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Behind the scenes efi.system_table is a data structure efi.system_table.ConOut is a pointer to a protocol .contents dereferences a ctypes pointer Most EFI calls expect a “this” pointer ctypes converts "Hello world\r\n" to a Unicode string

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Behind the scenes efi.system_table is a data structure efi.system_table.ConOut is a pointer to a protocol .contents dereferences a ctypes pointer Most EFI calls expect a “this” pointer ctypes converts "Hello world\r\n" to a Unicode string ctypes returns the error code from EFI

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Resource management EFI uses manual memory management

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Resource management EFI uses manual memory management Python uses garbage collection

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Resource management EFI uses manual memory management Python uses garbage collection Python GC doesn’t know about references from EFI

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Resource management EFI uses manual memory management Python uses garbage collection Python GC doesn’t know about references from EFI Must keep Python object alive as long as EFI references it

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Resource management EFI uses manual memory management Python uses garbage collection Python GC doesn’t know about references from EFI Must keep Python object alive as long as EFI references it Must explicitly free EFI resources when no longer referenced from Python

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EFI networking protocols EFI_IP4_CONFIG2_PROTOCOL

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EFI networking protocols EFI_IP4_CONFIG2_PROTOCOL Read current IP configuration, or start IP configuration

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EFI networking protocols EFI_IP4_CONFIG2_PROTOCOL Read current IP configuration, or start IP configuration EFI_TCP4_SERVICE_BINDING_PROTOCOL

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EFI networking protocols EFI_IP4_CONFIG2_PROTOCOL Read current IP configuration, or start IP configuration EFI_TCP4_SERVICE_BINDING_PROTOCOL Create a new EFI_TCP4_PROTOCOL, like socket()

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EFI networking protocols EFI_IP4_CONFIG2_PROTOCOL Read current IP configuration, or start IP configuration EFI_TCP4_SERVICE_BINDING_PROTOCOL Create a new EFI_TCP4_PROTOCOL, like socket() EFI_TCP4_PROTOCOL

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EFI networking protocols EFI_IP4_CONFIG2_PROTOCOL Read current IP configuration, or start IP configuration EFI_TCP4_SERVICE_BINDING_PROTOCOL Create a new EFI_TCP4_PROTOCOL, like socket() EFI_TCP4_PROTOCOL EFI socket API: Configure, Connect, Accept, Transmit, Receive, Close

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EFI networking protocols EFI_IP4_CONFIG2_PROTOCOL Read current IP configuration, or start IP configuration EFI_TCP4_SERVICE_BINDING_PROTOCOL Create a new EFI_TCP4_PROTOCOL, like socket() EFI_TCP4_PROTOCOL EFI socket API: Configure, Connect, Accept, Transmit, Receive, Close

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EFI networking protocols EFI_IP4_CONFIG2_PROTOCOL Read current IP configuration, or start IP configuration EFI_TCP4_SERVICE_BINDING_PROTOCOL Create a new EFI_TCP4_PROTOCOL, like socket() EFI_TCP4_PROTOCOL EFI socket API: Configure, Connect, Accept, Transmit, Receive, Close Glossing over quirks, bugs, error handling, workarounds, and compatibility with older versions

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Impedance mismatch: select versus Receive/Accept select checks for pending data or connections

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Impedance mismatch: select versus Receive/Accept select checks for pending data or connections Does not read data or accept connection

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Impedance mismatch: select versus Receive/Accept select checks for pending data or connections Does not read data or accept connection EFI can only check for data by calling Receive with a valid buffer

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Impedance mismatch: select versus Receive/Accept select checks for pending data or connections Does not read data or accept connection EFI can only check for data by calling Receive with a valid buffer Solution: buffer received data, call Receive when buffer empty

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Impedance mismatch: select versus Receive/Accept select checks for pending data or connections Does not read data or accept connection EFI can only check for data by calling Receive with a valid buffer Solution: buffer received data, call Receive when buffer empty Likewise for Accept

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Impedance mismatch: select versus Receive/Accept select checks for pending data or connections Does not read data or accept connection EFI can only check for data by calling Receive with a valid buffer Solution: buffer received data, call Receive when buffer empty Likewise for Accept Similar to the implementation of sockets in an OS kernel

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Impedance mismatch: Poll EFI_TCP4_PROTOCOL not updated directly from low-level interrupts

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Impedance mismatch: Poll EFI_TCP4_PROTOCOL not updated directly from low-level interrupts Data processed infrequently, even with asynchronous call running

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Impedance mismatch: Poll EFI_TCP4_PROTOCOL not updated directly from low-level interrupts Data processed infrequently, even with asynchronous call running Caller expected to call Poll periodically if waiting

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Impedance mismatch: Poll EFI_TCP4_PROTOCOL not updated directly from low-level interrupts Data processed infrequently, even with asynchronous call running Caller expected to call Poll periodically if waiting Improves performance by orders of magnitude

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Impedance mismatch: Poll EFI_TCP4_PROTOCOL not updated directly from low-level interrupts Data processed infrequently, even with asynchronous call running Caller expected to call Poll periodically if waiting Improves performance by orders of magnitude Solution: call Poll inside helpers for select

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Impedance mismatch: asynchronous callbacks All EFI socket calls asynchronous

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Impedance mismatch: asynchronous callbacks All EFI socket calls asynchronous Calls take a “completion token” with EFI_EVENT to signal when done

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Impedance mismatch: asynchronous callbacks All EFI socket calls asynchronous Calls take a “completion token” with EFI_EVENT to signal when done For sockets, EFI_EVENT must have a callback function

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Impedance mismatch: asynchronous callbacks All EFI socket calls asynchronous Calls take a “completion token” with EFI_EVENT to signal when done For sockets, EFI_EVENT must have a callback function Need to handle callback safely from Python

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Python concurrency model Python expects bytecode ops and C calls to run to completion

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Python concurrency model Python expects bytecode ops and C calls to run to completion Global Interpreter Lock (GIL)

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Python concurrency model Python expects bytecode ops and C calls to run to completion Global Interpreter Lock (GIL) Data may have inconsistent state when callback occurs

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Python concurrency model Python expects bytecode ops and C calls to run to completion Global Interpreter Lock (GIL) Data may have inconsistent state when callback occurs Almost all CPython functions prohibited

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Python concurrency model Python expects bytecode ops and C calls to run to completion Global Interpreter Lock (GIL) Data may have inconsistent state when callback occurs Almost all CPython functions prohibited Same problem arises with Ctrl-C and signals

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Py_AddPendingCall Register a callback (with context)

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Py_AddPendingCall Register a callback (with context) Python calls it at the next safe point

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Py_AddPendingCall Register a callback (with context) Python calls it at the next safe point Can call arbitrary CPython functions from the callback

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Handling events C module provides event callback function pointer

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Handling events C module provides event callback function pointer Python code creates EFI_EVENT with C callback

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Handling events C module provides event callback function pointer Python code creates EFI_EVENT with C callback C callback invokes universal Python callback

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Handling events C module provides event callback function pointer Python code creates EFI_EVENT with C callback C callback invokes universal Python callback Python callback dispatches to event-specific callback via dict

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Handling events C module provides event callback function pointer Python code creates EFI_EVENT with C callback C callback invokes universal Python callback Python callback dispatches to event-specific callback via dict dict keeps Python objects live while EFI_EVENT references them

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Implementing select Takes read and write lists of sockets

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Implementing select Takes read and write lists of sockets Or file descriptors; map to sockets via dict

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Implementing select Takes read and write lists of sockets Or file descriptors; map to sockets via dict Loop over sockets until timeout expires

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Implementing select Takes read and write lists of sockets Or file descriptors; map to sockets via dict Loop over sockets until timeout expires Call _read_ready or _write_ready

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Implementing select Takes read and write lists of sockets Or file descriptors; map to sockets via dict Loop over sockets until timeout expires Call _read_ready or _write_ready _read_ready checks queue, calls Receive or Accept

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Implementing select Takes read and write lists of sockets Or file descriptors; map to sockets via dict Loop over sockets until timeout expires Call _read_ready or _write_ready _read_ready checks queue, calls Receive or Accept If already running from previous call, call Poll

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Implementing select Takes read and write lists of sockets Or file descriptors; map to sockets via dict Loop over sockets until timeout expires Call _read_ready or _write_ready _read_ready checks queue, calls Receive or Accept If already running from previous call, call Poll Handle connection closure to provide EOF from recv

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Implementing select Takes read and write lists of sockets Or file descriptors; map to sockets via dict Loop over sockets until timeout expires Call _read_ready or _write_ready _read_ready checks queue, calls Receive or Accept If already running from previous call, call Poll Handle connection closure to provide EOF from recv Queues data or error when callback called

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Implementing select Takes read and write lists of sockets Or file descriptors; map to sockets via dict Loop over sockets until timeout expires Call _read_ready or _write_ready _read_ready checks queue, calls Receive or Accept If already running from previous call, call Poll Handle connection closure to provide EOF from recv Queues data or error when callback called _write_ready returns true if connected

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Implementing select Takes read and write lists of sockets Or file descriptors; map to sockets via dict Loop over sockets until timeout expires Call _read_ready or _write_ready _read_ready checks queue, calls Receive or Accept If already running from previous call, call Poll Handle connection closure to provide EOF from recv Queues data or error when callback called _write_ready returns true if connected Always calls Poll if connected

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class socket __init__: Create EFI_TCP4_PROTOCOL from binding protocol

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class socket __init__: Create EFI_TCP4_PROTOCOL from binding protocol __del__/close: Cancel all outstanding callbacks

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class socket __init__: Create EFI_TCP4_PROTOCOL from binding protocol __del__/close: Cancel all outstanding callbacks connect: Call Configure and Connect

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class socket __init__: Create EFI_TCP4_PROTOCOL from binding protocol __del__/close: Cancel all outstanding callbacks connect: Call Configure and Connect recv: Return data from queue

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class socket __init__: Create EFI_TCP4_PROTOCOL from binding protocol __del__/close: Cancel all outstanding callbacks connect: Call Configure and Connect recv: Return data from queue Spin on _read_ready if queue empty; this starts a Receive

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class socket __init__: Create EFI_TCP4_PROTOCOL from binding protocol __del__/close: Cancel all outstanding callbacks connect: Call Configure and Connect recv: Return data from queue Spin on _read_ready if queue empty; this starts a Receive sendall: Call Transmit; save status for

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class socket __init__: Create EFI_TCP4_PROTOCOL from binding protocol __del__/close: Cancel all outstanding callbacks connect: Call Configure and Connect recv: Return data from queue Spin on _read_ready if queue empty; this starts a Receive sendall: Call Transmit; save status for bind: Save provided address and port for later calls

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class socket __init__: Create EFI_TCP4_PROTOCOL from binding protocol __del__/close: Cancel all outstanding callbacks connect: Call Configure and Connect recv: Return data from queue Spin on _read_ready if queue empty; this starts a Receive sendall: Call Transmit; save status for bind: Save provided address and port for later calls listen: Call Configure for listening socket

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class socket __init__: Create EFI_TCP4_PROTOCOL from binding protocol __del__/close: Cancel all outstanding callbacks connect: Call Configure and Connect recv: Return data from queue Spin on _read_ready if queue empty; this starts a Receive sendall: Call Transmit; save status for bind: Save provided address and port for later calls listen: Call Configure for listening socket accept: Return queued connection if any

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class socket __init__: Create EFI_TCP4_PROTOCOL from binding protocol __del__/close: Cancel all outstanding callbacks connect: Call Configure and Connect recv: Return data from queue Spin on _read_ready if queue empty; this starts a Receive sendall: Call Transmit; save status for bind: Save provided address and port for later calls listen: Call Configure for listening socket accept: Return queued connection if any Spin on _read_ready if queue empty; this starts an Accept

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Socket demo and walkthrough

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High-level client demo

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High-level server demo

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Try it out yourself BITS: https://biosbits.org/

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Try it out yourself BITS: https://biosbits.org/ QEMU/KVM

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Try it out yourself BITS: https://biosbits.org/ QEMU/KVM Client works automatically

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Try it out yourself BITS: https://biosbits.org/ QEMU/KVM Client works automatically For server, use hostfwd option to forward ports inside

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Try it out yourself BITS: https://biosbits.org/ QEMU/KVM Client works automatically For server, use hostfwd option to forward ports inside OVMF: Open Virtual Machine Firmware, EFI for QEMU

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Try it out yourself BITS: https://biosbits.org/ QEMU/KVM Client works automatically For server, use hostfwd option to forward ports inside OVMF: Open Virtual Machine Firmware, EFI for QEMU Or try it on physical hardware

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Try it out yourself BITS: https://biosbits.org/ QEMU/KVM Client works automatically For server, use hostfwd option to forward ports inside OVMF: Open Virtual Machine Firmware, EFI for QEMU Or try it on physical hardware Check BIOS settings to enable EFI network stack

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Try it out yourself BITS: https://biosbits.org/ QEMU/KVM Client works automatically For server, use hostfwd option to forward ports inside OVMF: Open Virtual Machine Firmware, EFI for QEMU Or try it on physical hardware Check BIOS settings to enable EFI network stack Use wired Ethernet

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BIOS Implementation Test Suite (BITS) http://biosbits.org/ Questions?

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Networking without an OS Demo Backup Josh Triplett josh@joshtriplett.org PyCon 2016

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